From the prior art familiar to applicants, it is known that the control variable is the surface velocity of the take-up mechanisms (tire or drum) employed during the wrapping operation. This is in contrast to the present invention, (as will be detailed hereinafter) where the take-up motor speed is directly controlled without sensing the surface velocity or tension of the loop. It follows that with the present invention, it is not necessary to have the rubber present for the control system to function. The most apparent advantage is employing this type of control is that all errors involved with the sensing of rubber, as well as errors in weight which have to do with variations in take-up (tire) diameter, are eliminated. By the present invention, material build-up of a constant weight independent of surface variations is attainable.
None of the dancers or loop control systems of prior art equipment operate in a similar fashion. This departure from the prior art is quite significant and represents a clear advantage in the field of technology. What makes the present invention important it that one would not normally assume that control without sensing tension is more accurate than with sensing the tension of the feed material; this, of course, assumes that the cross-section geometry of the raw material is constant.
In further contrast to the present invention, the prior art, such as shown and disclosed in U.S. Pat. No. 3,610,496, employs an arrangement for web tension control necessitating a dependent input velocity, for an example, a controllable input, and functions through a series of mechanical assemblies, whereby the input and output shafts are controlled through the drive belt ratio. This prior art patent employs electrical pulses for mechanical adjustment of a pulley to control the belt drive reducer position and hence speed ratio is attained. The limitations inherent to this prior art, only permits its use on solid or non-stretchable web materials (not rubber ribbon). In contrast to the aforementioned, the present invention functions through an independent input velocity in which the output shaft is only controlled as a function of the input shaft velocity and ratio selected. This being accomplished through electronic counting and voltage control through an amplifier/controller of a DC motor with the result that motor speed is controlled directly. A more detailed discussion follows hereinafter. Of interest is the fact that with the present invention, shaft velocity synchronization can be attained with both elastomeric and non-plastic web materials.
In conclusion, the very nature of the present invention as employed with the deposition of rubber ribbon does not afford the control of input velocity in any fashion as is disclosed in the prior art. Hence, with the present invention only output velocity is controlled to effect synchronization of shaft velocities. It follows that with the teachings of prior art such as U.S. Pat. No. 3,610,496 one could not apply such control systems for the present intended purpose.
The present invention can operate with an apparatus of the type shown and disclosed in U.S. Pat. Nos. 3,251,722 and 3,308,000. In particular, the required rotational velocities are synchronized by means of the present invention.
The main object of the present invention is to overcome the defects of the prior art.
Still another object of the present invention is to employ an apparatus which will enable the tire treading operation to take place at maximum obtainable extrusion rates.
Still a further object of the present invention is to provide an apparatus and method which will permit complete tire profile control on a repeatable basis for any given production run.
Still other advantages of the present invention will be best understood with respect to the specification, claims and accompanying drawings.